"Is it stand-up or journalism?" a critic recently asked of Mark Thomas's act. Actually, it is both. And, not having seen Thomas on stage since his early days, I was impressed by his ability to combine campaigning zeal with comic technique: it is not often you come out of a stand-up show feeling better informed, as well as having had a good time.
Thomas's current show, which is halfway through a national tour, consists of two hour-long sets. In the first, Thomas tackles the absurdity of the law which obliges protesters around Parliament Square to obtain advance police permission. He did this by getting masses of individuals to demand multiple licences, shifting the sites of the demonstrations and swamping the police in paperwork. In making his point, Thomas sometimes lapses into glib generalisations such as that all politicians are "venal, self-serving scum", but also reveals a wry humour. Lamenting that one particular group turned up without the approved licence, he observes, "That's anarchists for you."
But Thomas gets his teeth into even stronger material in his second-half assault on the arms trade and what he calls "the widgets of barbarity". It is good to be reminded of the stark facts: that the UK arms industry is subsidised to the tune of £850m a year, and that Britain is the world's second biggest arms dealer. Thomas also got his hands dirty by going to arms fairs, exposing the illegal trade in electroshock weapons and, at one point, taking part in a sting to reveal the sale of military trucks to the Sudanese government.
Thomas's reflex contempt for politicians is somewhat undermined by the fact that it was a parliamentary committee, rather than TV or the press, that took action on the Sudanese issue. But Thomas proves that a conscience-driven comic can go where investigative reporters fear to tread. Mixing moral fervour with open-eyed mockery, he also shows, through his exposure of the laxly policed arms trade, that comedy is itself a potent weapon for change.
· At the Tricycle tonight. Box office: 0207-328 1000. Then touring.
